Exposure blending

[A_S]

I've been messing about with 2 exposures I took tonight - one exposed for the sky and one for the trees and I tried to blend both exposures:

 

exposure blend v1 by Andrew_S84, on Flickr

 

I think it turned out well although the camera orientation must have been slightly different between the 2 as the post was at a slightly different angle and trees slightly shifted to the right. So I had to get rid of the post (the post can be seen in the autumn pictures thread) and do a lot of work on the blend. It is by no means perfect but for a first ever attempt I think it is ok.

 

Tutorial I used is here (plus my own knowledge of alpha mapping and photoshop).

 

http://blog.summersound.co.uk/2011/02/exposure-blending-tutorial.html

 

Andy

[A_S]

I've been meaning to try it for ages but thought it might be a bit fiddly - however the method of generating the mask in the tutorial above is fantastic.

 

041013 exposure blend by Andrew_S84, on Flickr

I took these a few weeks ago and because of the dynamic range at the time, even with the combination of a 3 stop soft grad filter and 2 stop hard I couldn't expose for the trees, however by combining this with an image taken immediately after and exposed for the trees (sky was pretty white) I can get a more accurate tree line/image than the camera could capture.

 

I'm keen to see if anyone else has any tips/examples of blending exposures or focus stacking etc?

 

Andy

[Steadfast]

Thanks for sharing the link Andy (and lovely landscapes too btw), I've had a play with a picture that has troubled me since I initially processed the raw in May. I'm still not 100% happy, but I feel its an improvement over the original image. Rather than using two images, I've created two exposures from the same raw file, one for the sky, the other for the rest of the image, since it's a moving subject in the picture.

So, here's the original, which used a gradient and brush exposure in the sky to darken it to give cloud detail, but due to the fiddly edges of the trees it was impossible to do so without darkening the edges of them. This is particularly bad to the left of the loco.

So here's the blended version. I used exactly the method outlined in the video linked in Andy's post. It took me a fair while, playing with different levels to create the alpha mask that gave the best results, but that was what I expected for a first attempt at it.

There's an area where the trees are lost in the cloud of flyash coming from the wagons that I spent ages, literally hours, editing various outputs from the RGB channels to create an alpha channel that separated this from the sky satisfactorily. It's around the telegraph pole, above the second wagon. In the end I cheated a little by combining two 'least worse' results, though I've included the crop below to highlight this. It's still something I want to work on some more, so this is still very much a work in progress at the moment, I think I'll see if any tips for dealing with problem areas exist online.

As I said though, despite this problem area, I'm happy with it for a first attempt and I'm going to try it on some other, easier pictures and see if I can find further information online to get a better result on this one.

Thanks again to Andy for the original post, it kept me entertained for the last few days and will help me get some better looking pictures!

 

jo

[A_S]

It is very good Jo - The thing you have to remember that you know where all the problems are and others don't if you hadnt have mentioned about the trees etc I wouldnt have noticed even on the original edit.

 

The thing I find hard is trees like the one on the left - trying to get the alpha channel to pick up the detail of individual branches satisfactorily otherwise some of the leaves look like have been cut out and stuck there - but you have done very well on your version.

 

One thing that may help with the flyash that I found on the trees is by using the brush and messing around with the hardness setting/the flow setting and opacity.

 

Opacity - I like to think as the "see throughness". When set on black as your main colour 100% opacity means you are painting full black, 50% grey and 0% a very very thin layer that you can just about see. Obviously in this case by painting at less opacity you are blending the 2 images (or versions of the same raw) where as at 100% you are revealing one fully and hiding the other.

 

Flow - I like to think of flow as an airbrush. at 100% its a thick covering of the selected colour - by reducing this its like doing several thin coats to build up a good even finish. Therefore by reducing the flow you increase the control and can blend gradually bit by bit, where you think you need to work slowly or carefully.

 

Hardness - Hardness is how intense the colour is accross the radius of the circle. The more you reduce hardness the less intense the brush is towards the extremities of its diameter/radius, a hardness of 100% means the intensity is the same at the centre as at the circumference take that to 50% and the outsides are less intense but you sill get 100% intensity in the middle - like a graduated brush really.

 

These can be used to blend areas where you want to mix the foreground and background exposure, like with the wagons or with the leafs on the trees. Hardness is really good with edges but you have to be carefully not to leave "halos" of areas such as the sky in the tree images appearing around the edges when you really want the image edited for the sky to appear, i.e where the fore and background image join and settings such as the opacity can help avoid these by reducing the intensity of the blend and futher control like airburshing it on gradually can be gained by using flow.

 

I might be teaching you to such eggs there Jo, but I hope it helps. I may post one of my layer masks to illustrate. Also I've had a few Chamay's so I hope it reads ok..!

[Steadfast]

Hi Andy

Don't for one second think of it as egg sucking! It's nice to have confirmation what I've taught myself is up the right street!

I did use a bit of brush work on the mask to soften some edges and blend some areas, definitely helped a lot in the difficult tree and flyash area.

The tree to the left was surprisingly chunky when looked at at full resolution, I think the strong wind blowing that day helped to bunch the leaves into fair size 'lumps'. It took two or three attempts at the alpha channel to get that area to reproduce correctly. Once I had one that worked well here, I created a second one that worked well for the trees in the background above the wagons. The two black and white images were then joined together before creating an alpha channel with them. This isn't mentioned on the video, so I'm not sure if its an 'approved' technique but it worked for me. Also his outline was a lot simpler so a single image worked for the alpha channel throughout

 

jo